1. Field of the Invention
The present invention relates to a novel curable composition. More particularly, the present invention relates to a curable composition having excellent curing properties and providing a cured product having a good hydrophilic property and an excellent dimensional reproducibility, which is especially valuable as a dental impression material.
2. Description of the Related Art
A curable composition which is cured at normal temperature to provide a cured body having a rubbery elasticity is widely used as a dental impression material, a sealing material and the like. When this curing composition is used as a dental impression material, in order to increase the affinity with the surfaces of teeth and gingiva for obtaining precise impressions, a cured body of the curable composition is required to have a good hydrophilic property. Furthermore, in this use, the curable composition is required to be excellent in such a curing property that the curable composition is uniformly cured even to a deep portion in a short time (hereinafter referred to as "deep portion curing property"), and a cured body of the curable composition is required to have a good dimensional reproducibility without any plastic deformation at the time of removing the cured body from a mold.
As the curable composition having a good hydrophilic property and being excellent in the deep portion curing property, there has been proposed a composition comprising a polyether having alkenyl groups, a polyorganohydrogen-siloxane having a Si-H group and a platinum complex catalyst (see Japanese patent application laid-open specifications No. 78055/80 and No. 55056/85). Although this composition is excellent in the deep portion curing property and hydrophilic property, the compatibility between the polyether and the polyorganohydrogen-siloxane is poor and a completely cured body is hardly obtained. Accordingly, if this curable composition is used as a dental impression material, plastic deformation is caused when the cured body is removed from a mold, and therefore, a precise impression cannot be obtained. It is considered that the compatibility between the polyether and the polyorganohydrogen-siloxane will be improved by modifying the polyorganohydrogen-siloxane with a polyether. However, in case of this composition, since the free terminals of the polyether used for modification acts as a plasticizer in the cured body, the surface of the cured body becomes sticky and there is a risk of occurrence of plastic deformation, and therefore, the composition cannot be practically used. In short, a satisfactory curable composition has not been developed.